Sintered body and production method thereof

ABSTRACT

An object is to provide a sintered body causing less chipping and having a sufficiently higher polishing rate than a conventional AlTiC sintered body, and providing a sufficiently smooth air bearing surface. The sintered body according to the present invention consists of Al 2 O 3 , a compound represented by the chemical formula (1) below, and a composite oxide containing Al and Ti, 
       TiC x O y   (1) 
     wherein x+y≦1, x&gt;0 and y&gt;0.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sintered body and, more particularly,to a sintered body suitable for a magnetic head slider, and a productionmethod thereof.

2. Related Background Art

A hard disk drive (HDD) is equipped with a magnetic head slider forwriting and reading information onto and from a hard disk. Recently, themagnetic head slider is also being downsized with increase in recordingdensity and reduction in size of the hard disk drive.

The magnetic head slider has a configuration in which a magnetic head ismounted on a substrate, and this substrate is generally composed of aceramic sintered body. The ceramic sintered body for the substraterecently commonly known is a high-strength sintered body consistingprimarily of alumina and titanium carbide, so called an AlTiC sinteredbody (cf. Japanese Patent Application Laid-open No. 8-34662).

SUMMARY OF THE INVENTION

For further downsizing of the magnetic head slider, it is necessary toimprove accuracy of microfabrication of the magnetic head slider.Specifically, when an air inlet groove is formed by processing an airbearing surface of the magnetic head slider, it is required to suppresschipping (cracking) at a processed part. The reason for it is that asthe magnetic head slider becomes smaller, the chipping of the magnetichead slider tends to more significantly interfere with control of a flyheight (height of the magnetic head relative to the hard disk) and hasraised the possibility of crash between the magnetic head and the harddisk.

Furthermore, the fly height is also decreasing with increase inrecording density and reduction in size of the hard disk drive. However,the crash becomes more likely to occur as the fly height decreases. Forenabling further decrease of the fly height, therefore, it is needed tosuppress the chipping of the magnetic head slider to improvecontrollability of the fly height and prevent the crash.

In addition, for producing the magnetic head slider using the AlTiCsintered body, a generally adopted method is to lay a laminate includingthe magnetic head, on the substrate of the AlTiC sintered body, to cutthe resultant body in parallel with a lamination direction to form anexposed surface of the magnetic head, and to polish (or lap) thisexposed surface to form the air bearing surface.

In the conventional method, a polishing rate of the substrate (AlTiCsintered body) is lower in the polishing step than that of the laminateincluding the magnetic head and thus a polishing amount of the laminateis larger than that of the substrate, which leads to a tendency to makea large level difference in the air bearing surface between thesubstrate and the laminate. This level difference is undesirable becauseit makes the control of the fly height difficult. There is, therefore, ademand for reducing the level difference in the air bearing surfacecaused by the difference between the polishing rates of the substrateand the laminate laid on the substrate, in the lapping step and therebysmoothing the air bearing surface.

In the production of the magnetic head slider, the air bearing surfaceis processed by ion milling, which is a kind of dry etching, to form theair inlet groove, and for improving the controllability of the flyheight, it is also required to further lower the surface roughness ofthe air bearing surface processed by dry etching (which will besometimes referred to as “dry etched surface”) and thereby to smooth thedry etched surface.

The present invention has been accomplished in view of the abovecircumstances and an object of the present invention is to provide asintered body causing less chipping and having a sufficiently higherpolishing rate than the conventional AlTiC sintered body, and providinga sufficiently smooth air bearing surface, and a production method ofthe sintered body.

In order to achieve the above object, a sintered body according to thepresent invention is one consisting of Al₂O₃, a compound represented bythe chemical formula (1) below (which will be sometimes referred to as“TiC_(x)O_(y)”), and a composite oxide containing Al and Ti. Namely, thesintered body according to the present invention consists of threephases, a phase consisting of Al₂O₃, a phase consisting of TiC_(x)O_(y),and a phase consisting of the composite oxide of Al and Ti. The“compound represented by the chemical formula (1) below” in the presentinvention is a compound which consists of Ti, C, and O and an averagecomposition of which is expressed by the chemical formula (1) below. Inother words, in the present invention, local compositions of the phaseof TiC_(x)O_(y) may deviate from the composition represented by thechemical formula (1) below but the average composition of the entirephase of TiC_(x)O_(y) is represented by the chemical formula (1) below:

TiC_(x)O_(y)  (1)

wherein x+y≦1, x>0 and y>0.

The sintered body of the present invention causes less chipping in themagnetic head slider and has a sufficiently higher polishing rate thanthe conventional AlTiC sintered body, and provides a sufficiently smoothair bearing surface.

It was found by the Inventors' research that since the sintered body ofthe present invention had the phase consisting of the composite oxidecontaining Al and Ti, in addition to the phase consisting of Al₂O₃ andthe phase consisting of TiC_(x)O_(y), occurrence of chipping was moresuppressed than in the case where the sintered body was composed of thetwo phases of the phase consisting of Al₂O₃ and the phase consisting ofTiC_(X)O_(y).

It was also found by the Inventors' research that the whole air bearingsurface was more likely to be evenly etched in the step of processingthe air bearing surface by ion milling being a kind of dry etching andthe dry etched surface was more likely to smooth than in the case wherethe sintered body further had a phase consisting of another compound(e.g., carbon), in addition to the phase consisting of Al₂O₃ and thephase consisting of TiC_(x)O_(y).

The foregoing sintered body of the present invention preferablysatisfies the condition of 0.3<y≦0.52.

As the molar ratio y of oxygen in TiC_(x)O_(y) becomes smaller, there isa tendency to reduce the effect of increasing the polishing rate of thesintered body or the effect of suppressing the occurrence of chipping.Furthermore, the sintered body with larger y is more likely to deform ina firing step in its production and, with use of such a sintered body,there is a tendency to make it difficult to produce the magnetic headslider required to have the smooth air bearing surface. In contrast toit, the sintered body of the present invention can reduce thesetendencies when it satisfies the condition of 0.3<y≦0.52.

The present invention provides a suitable production method of theaforementioned sintered body of the present invention. Namely, a methodfor producing the sintered body according to the present inventioncomprises a step of hot pressing a raw material powder containing Al₂O₃,TiC and TiO₂, under a pressure in the range of 100 to 200 kgf/cm². Itshould be noted that in the present invention the “hot press” means tofire the raw material powder under pressure (compression) by a uniaxialpressing method.

This production method allows us to obtain the aforementioned sinteredbody of the present invention having the above-described configuration,causing less chipping and having the sufficiently higher polishing ratethan the conventional AlTiC sintered body, and providing thesufficiently smooth air bearing surface.

In the foregoing production method of the sintered body of the presentinvention, a content of TiO₂ in the raw material powder is preferably inthe range of 12 to 24% by mass.

This makes it possible to obtain the sintered body of the presentinvention where 0.3<y≦0.52.

The present invention successfully provides the sintered body causingless chipping and having the sufficiently higher polishing rate than theconventional AlTiC sintered body, and providing the sufficiently smoothair bearing surface, and the production method of this sintered body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an enlarged sectional configurationof a sintered body according to a preferred embodiment.

FIG. 2 is a perspective view showing a magnetic head slider according toa preferred embodiment.

FIG. 3 is a schematic sectional view along line II-II of the magnetichead slider shown in FIG. 2.

FIG. 4 is a perspective view showing a substrate made in a disk wafershape of a sintered body.

FIG. 5 is a perspective view subsequent to FIG. 4 for explaining aproduction method of the magnetic head slider.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be describedbelow with reference to the drawings.

[Sintered Body]

First, the sintered body according to a preferred embodiment will bedescribed.

The sintered body of the present embodiment is an AlTiC sintered bodyconsisting of three phases, a crystal phase of Al₂O₃ (alumina), acrystal phase of a compound represented by the chemical formula (1)below, and a crystal phase of a composite oxide containing Al and Ti(which will be sometimes referred to as “Al—Ti—O”). It is noted hereinthat the sintered body is one obtained by sintering a combination of rawmaterials of these components, as described below.

TiC_(x)O_(y)  (1)

wherein x+y≦1, x>0 and y>0.

In the case of x+y=1, the crystal phase of TiC_(x)O_(y) is oneconsisting of TiCO. In the case of x+y<1, the crystal phase is oneconsisting of TiCO with vacancies due to partial loss of C or O. In thecase of x+y>1, the rock salt type crystal structure cannot be maintainedand thus workability of the sintered body tends to worsen; however, thepresent embodiment suppresses this tendency because x+y≦1. For achievingthe effect of the present invention more definitely, it is preferable tosatisfy the condition of 0.5<x+y.

In the present embodiment, preferably, 0.3<y≦0.52.

As the molar ratio y of oxygen in TiC_(x)O_(y) becomes smaller, there isa tendency to reduce the effect of increasing the polishing rate of thesintered body or the effect of suppressing the occurrence of chipping inthe magnetic head slider. Furthermore, the sintered body with larger yis more likely to deform in a firing step in its production and there isa tendency to make it difficult to produce the magnetic head slider. Incontrast to it, the present embodiment reduces these tendencies because0.3<y≦0.52.

FIG. 1 is a schematic view showing an enlarged sectional configurationof the sintered body of the preferred embodiment. As shown in FIG. 1,the sintered body 2 is composed of three types of crystal grains,crystal grains 110 of Al₂O₃, crystal grains 120 of TiC_(x)O_(y), andcrystal grains 140 of Al—Ti—O.

A mean diameter of the crystal grains 110 of Al₂O₃ in the sintered bodyis, for example, in the range of 0.05 to 1.0 μm and a mean diameter ofthe crystal grains 120 of TiC_(x)O_(y) is, for example, in the range of0.05 to 0.5 μm. A mean diameter of the crystal grains 140 of Al—Ti—O is,for example, in the range of 0.05 to 1.0 μm. These mean diameters ofcrystal grains can be determined, for example, as follows. First, thesintered body is fractured and its fractured surface is mirror finishedand thermally etched at a temperature of (sintering temperature−100)° C.The surface is photographed at the magnification of 30000× with ascanning electron microscope and straight lines are radially drawn onthe photograph. Specifically, on the rectangular photograph of 9 mmvertical×12 mm horizontal, a vertical straight line, a horizontalstraight line, and two diagonal straight lines are drawn so as to pass acenter of the photograph (the total length of the straight lines is 51mm). Then the number of intersections where each straight line crossescrystal grain boundaries is counted and each of the mean diameters ofthe respective crystal grains can be determined by calculation of (totalextension of straight lines (mm))/(total number ofintersections×magnification of photograph).

In the sintered body of the present embodiment, the lattice constant ofTiC_(x)O_(y) is preferably less than 432.0 pm (picometer). This achievesmore definite improvement in the polishing rate of the sintered body.The lattice constant of TiC_(x)O_(y) in the present specification is,for example, that of the crystal grains of TiC_(x)O_(y) described above,and can be measured as follows. Specifically, first, a measurementsample obtained by pulverizing the sintered body is mixed with astandard sample of Si (e.g., silicon powder for a physical anglestandard: RSRP-43275G) and the mixture is subjected to X-ray measurementin the range of 2θ=15 to 90°. This measurement result is corrected forthe angle of 2θ from a diffraction line of Si of the standard sampleobserved with the measurement sample. After the angle correction, thelattice constant of space group Fm3m (crystal structure of TiC_(x)O_(y))is then determined. This lattice constant can be calculated using apredetermined analysis software application, e.g., JADE ver. 5 availablefrom Rigaku Corporation. A diffraction line of the (2,2,2) face of spacegroup Fm3m around 2θ=76° overlaps the diffraction line of Si and thusthese diffraction lines are not used for the correction for the angle of2θ and the calculation of the lattice constant.

The sintered body 2 of the present embodiment is preferably one whereina value of TiC_(x)O_(y)/Al₂O₃ being a peak area ratio of TiC_(x)O_(y) toAl₂O₃ is between 1.3 inclusive and 2.18, based on measurement by X-raydiffraction (XRD). Specifically, the foregoing value ofTiC_(x)O_(y)/Al₂O₃ can be determined from a peak area ratio of the (111)plane around 2θ=36° of space group Fm3m of TiC_(x)O_(y) to the (104)plane around 2θ=35° of space group R3-C of Al₂O₃ based on themeasurement by XRD. When the above condition is met, it becomes easierto reduce the occurrence of void and to suppress the occurrence ofchipping than in the case where the condition is not met.

The sintered body 2 of the present embodiment may contain a trace amountof another component not to affect the effect of the present invention,as needed, in addition to Al₂O₃, TiC_(x)O_(y), and Al—Ti—O. Theadditional component can be, for example, titania (TiO₂). Since TiO₂ isused as a raw material of the sintered body as described below, a traceamount of TiO₂ may remain in the sintered body 2. Furthermore, thecrystal grains 110 of Al₂O₃, the crystal grains 120 of TiC_(x)O_(y), andthe crystal grains 140 of Al—Ti—O may contain a trace amount of carbon.

[Production Method of Sintered Body]

A preferred embodiment of the production method of the aforementionedsintered body will be described below.

The first step is to prepare a raw material powder containing an Al₂O₃powder, a TiC powder, and a TiO₂ powder. With this, reaction takes placeamong the powders during a hot pressing step described below, to produceTiC_(x)O_(y) and Al—Ti—O in the sintered body.

A content of the TiO₂ powder in the raw material powder is preferablydetermined to be in the range of 12 to 24% by mass relative to the totalamount of the raw material powder. When the content of the TiO₂ powderis set in this range, the molar ratio y of oxygen in TiC_(x)O_(y) in theresultant sintered body can fall within the range of 0.3<y≦0.52.

If the content of the TiO₂ powder in the raw material powder is toosmall, the molar ratio y of oxygen in TiC_(x)O_(y) in the resultantsintered body becomes not more than 0.3 and there is a tendency toreduce the effect of increasing the polishing rate of the sintered body.

On the other hand, if the content of the TiO₂ powder in the raw materialpowder is too high, the molar ratio y of oxygen in TiC_(x)O_(y) in theresultant sintered body tends to become larger than 0.52. The shape ofthe sintered body with y larger than 0.52 can deform significantly fromthat of a compact before the hot press and it is sometimes difficult toproduce the magnetic head slider. In contrast to it, the presentembodiment defines the content of TiO₂ in the raw material powder as notmore than 24% by mass whereby y can be not more than 0.52; therefore,the sintered body can be prevented from deforming.

A content of the TiC powder in the raw material powder is preferably inthe range of 30 to 75 parts by mass, relative to 100 parts by mass ofthe Al₂O₃ powder. When the content of the TiC powder is in the foregoingrange, reaction becomes more likely to take place between the TiC powderand the TiO₂ powder in the raw material powder and the sintered body isformed at a preferred ratio of the Al₂O₃ crystal grains and theTiC_(x)O_(y) crystal grains, which facilitates implementation ofexcellent strength and electrical or thermal properties. If the contentof TiC is off this range, it might result in reducing the effect ofincreasing the polishing rate of the sintered body and the effect ofsuppressing the occurrence of chipping.

The next step is to mix the foregoing raw material powder, for example,in an organic solvent such as ethanol, IPA, or 95% denatured ethanol andthereby obtain a mixed powder. If water is used as a liquid to be mixedwith the raw material powder, the TiC powder will chemically react withwater to cause oxidation of the TiC powder; therefore, it is desirablenot to use water.

The mixing for obtaining the mixed powder can be implemented using aball mill or attritor. A mixing time is preferably in the range ofapproximately 10 to 100 hours. The media to be used in the mixing by theball mill or attritor can be, for example, alumina balls having thediameter in the range of about 1 to 20 mm.

Then the mixed powder is granulated by spray granulation. The spraygranulation is, for example, to spray dry the mixed powder in a hotblast of an inert gas such as nitrogen or argon containing little oxygenand thereby to obtain granules of the mixed powder. The granulation ispreferably carried out so that the grain sizes of the granules can be inthe range of about 50 to 200 μm. The temperature of the hot blast forspray drying is preferably in the range of about 60 to 200° C.

Thereafter, an organic solvent as described above is added into thegranules, as needed, to control a liquid content in the granules so thatthe organic solvent can be contained in the amount of about 0.1 to 10%by mass in the granules. In this process of controlling the liquidcontent in the granules, it is preferable not to use water as theliquid.

Then the granules are packed in a predetermined die and primarilycompacted, for example, by cold press to obtain a compact in apredetermined shape. There are no particular restrictions on the die aslong as it can compact the sintered body in the preferred shape; forexample, the die can be a disk forming die of metal or carbon having theinside diameter of about 150 mm. The unit pressure on the granules inthe cold press is in the range of approximately 50 to 150 kgf/cm²(approximately 5 to 15 MPa).

Next, the compact is hot pressed under the pressure in the range of 100to 200 kgf/cm² (about 10-20 MPa). Namely, the granules are fired whilethey are uniaxially compressed by a pair of punches opposed vertically.This induces the reaction among Al₂O₃, TiC and TiO₂ in the compact toobtain the sintered body consisting of three phases, the phase of Al₂O₃,the phase of TiC_(x)O_(y), and the phase of Al—Ti—O.

If the pressure on the compact by hot press is less than 100 kgf/cm², itbecomes difficult to produce the phase of Al—Ti—O in the sintered body.If the pressure on the compact by hot press is larger than 200 kgf/cm²,a phase consisting of carbon becomes likely to be made in the sinteredbody.

There are no particular restrictions on the shape of the sintered bodyobtained by hot press but the substrate is, for example, a disk orrectangular substrate having the diameter of 6 inches and the thicknessof about 2.5 mm. This allows the sintered body to be suitably applied tothe production of the magnetic head slider described below.

The firing temperature of the compact in hot press is preferably between1450° C. inclusive and 1700° C. When the firing temperature is set inthis range, it becomes easier to obtain the sintered body according tothe present embodiment. If the firing temperature is less than 1450° C.,sintering of the compact becomes insufficient, with the result that theresultant sintered body tends to include internal voids and thatgranules tend to drop during the lapping of the sintered body. On theother hand, if the firing temperature is not less than 1700° C., thecompact can deform during the firing and the production of the magnetichead slider can be harder. The firing temperate may be varied during thesintering.

The firing time of the compact in the hot press is preferably in therange of about 1 to 3 hours. This makes it easier to obtain the sinteredbody of the present embodiment.

The hot press of the compact is preferably carried out, for example, invacuum or in a nonoxidizing atmosphere such as an inert gas, e.g. Argas. When the compact is sintered in the nonoxidizing atmosphere, themolar ratio y of oxygen in TiC_(x)O_(y) in the resultant sintered bodycan be controlled more easily in the range of 0.3<y≦0.52.

[Magnetic Head Slider]

The following will describe the magnetic head slider using theabove-described sintered body. FIG. 2 is a perspective view showing themagnetic head slider of a preferred embodiment.

As shown in FIG. 2, the magnetic head slider 11 of the presentembodiment has a thin-film magnetic head 10 and is, for example, one tobe mounted on a hard disk drive (not shown) with a hard disk. This harddisk drive is configured to record and reproduce magnetic information ona recording surface of the hard disk rotating at a high speed, by thethin-film magnetic head 10.

The magnetic head slider 11 according to the embodiment of the presentinvention is of a nearly rectangular parallelepiped shape. In FIG. 2,the surface on the near side in the magnetic head slider 11 is a surfaceto be opposed to a recording medium, which is to be arranged opposite tothe recording surface of the hard disk, and is called an air bearingsurface (ABS) S. An air inlet groove 11 a is formed in the air bearingsurface S so as to extend in a direction perpendicular to a track widthdirection. The air inlet groove 11 a formed in the air bearing surface Simproves the controllability of the fly height (height of the thin-filmmagnetic head 10 relative to the hard disk). The forming position andshape of the air inlet groove 11 a do not have to be limited only tothose shown in FIG. 2.

While the hard disk rotates, the magnetic head slider 11 floats byvirtue of air flow caused by the rotation, whereby the air bearingsurface S is located away from the recording surface of the hard disk.The air bearing surface S may be coated with DLC (Diamond-Like Carbon)or the like.

This magnetic head slider 11 has a substrate 13 made of theaforementioned sintered body and a laminate 14 formed on this substrate13. This laminate 14 includes the thin-film magnetic head 10. In thepresent embodiment, the substrate 13 has a rectangular parallelepipedshape and the laminate 14 is formed on a side face of this substrate 13.

An upper face 14 a of the laminate 14 forms an end face of the magnetichead slider 11 and this upper face 14 a of the laminate 14 is providedwith recording pads 18 a, 18 b and reproducing pads 19 a, 19 b connectedto the thin-film magnetic head 10. The thin-film magnetic head 10 isprovided in the laminate 14 and is exposed in part from the air bearingsurface S to the outside. In FIG. 2, the thin-film magnetic head 10buried in the laminate 14 is indicated by solid lines in view of easierrecognition.

The magnetic head slider 11 of this configuration is mounted on a gimbalstructure 12 and is connected to an unrepresented suspension arm toconstitute a head gimbal assembly.

The structure of the magnetic head slider 11 will be described below inmore detail with reference to FIG. 3. FIG. 3 is a schematic sectionalview in the direction perpendicular to the air bearing surface S in themagnetic head slider 11 and to the track width direction (schematicsectional view along line II-II in FIG. 2). As described above, themagnetic head slider 11 has the substrate 13 of the nearly rectangularplate shape and the laminate 14 laid on the side face of the substrate13. The laminate 14 has the thin-film magnetic head 10 and a coat layer50 surrounding this thin-film magnetic head 10.

The thin-film magnetic head 10 has a GMR (Giant Magneto-Resistive)element 40 as a reading element for reading magnetic information on thehard disk, and an induction type electromagnetic conversion element 60as a writing element for writing magnetic information on the hard disk,in the order named from the near side to the substrate 13, and is thus acomposite thin-film magnetic head.

The electromagnetic conversion element 60 is one adopting the so-calledlongitudinal recording method, and is provided with a lower magneticpole 61 and an upper magnetic pole 64 in order from the substrate 13side and further with a thin-film coil 70.

The ends of the lower magnetic pole 61 and the upper magnetic pole 64 onthe air bearing surface S side are exposed in the air bearing surface Sand the exposed portions of the lower magnetic pole 61 and the uppermagnetic pole 64 are spaced from each other by a predetermined distanceto form a recording gap G. On the other hand, the end 64B of the uppermagnetic pole 64 on the far side from the air bearing surface S is benttoward the lower magnetic pole 61 and the end 64B is magneticallycoupled with the end of the lower magnetic pole 61 on the far side fromthe air bearing surface S. This configuration forms a magnetic circuitwith the gap G in between the upper magnetic pole 64 and the lowermagnetic pole 61.

The thin-film coil 70 is arranged so as to surround the end 64B of theupper magnetic pole 64 and generates a magnetic field in the recordinggap G by electromagnetic induction, thereby recording magneticinformation on the recording surface of the hard disk.

The GMR element 40 has a multilayer structure, which is not shown, isexposed in the air bearing surface S, and functions to detect a changein a magnetic field from the hard disk by making use of themagneto-resistance effect, to read magnetic information.

The insulating coat layer 50 is located between the GMR element 40 andthe electromagnetic conversion element 60 and between the upper magneticpole 64 and the lower magnetic pole 61 so as to separate them from eachother. The thin-film magnetic head 10 itself is also coated except forthe air bearing surface S with the coat layer 50. The coat layer 50 ismade mainly of an insulating material such as alumina. Specifically, thecoat layer is normally an alumina layer made by sputtering or the like.The alumina layer of this kind normally has an amorphous structure.

The thin-film magnetic head 10 may be of the perpendicular recordingmethod, instead of the longitudinal recording method. The GMR element 40may be replaced by an AMR (Anisotropic Magneto-Resistive) element makinguse of the anisotropic magneto-resistance effect, a TMR (Tunnel-typeMagneto-Resistive) element making use of the magneto-resistance effectoccurring at a tunnel junction, or the like.

Furthermore, the coat layer 50 may further include a magnetic layer orthe like for magnetically insulating the GMR element 40 and theelectromagnetic conversion element 60 from each other.

[Production Method of Magnetic Head Slider]

The following will describe a production method of the magnetic headslider 11 as described above.

The first step is, as shown in FIG. 4, to prepare the substrate 13 madein a disk wafer shape of the aforementioned sintered body of the presentembodiment. The next step is, as shown in FIG. 5( a), to lay a laminate14 including the thin-film magnetic heads 10 and coat layer 50, on thesubstrate 13 by a well-known method to obtain a multilayer structure100. The laminate 14 is formed herein so that a large number ofthin-film magnetic heads 10 are arrayed in a matrix in the laminate 14.

Then the multilayer structure 100 is cut in a predetermined shape andsize. In the present embodiment, for example, it is cut as indicated bydashed lines in FIG. 5( a) to form bars 100B in each of which aplurality of thin-film magnetic heads 10 are arranged in a line andthese thin-film magnetic heads 10 are arranged so as to be exposed in aside face 100BS, as shown in FIG. 5( b).

After formation of the bars 100B, the so-called lapping step is thencarried out to polish the side face 100BS of each bar 100B so as to formthe air bearing surface S. In this step, the substrate 13 and thelaminate 14 laid thereon are polished simultaneously and in a directionperpendicular to the lamination direction (i.e., in the direction ofarrow X in FIG. 3).

If the molar ratio y of oxygen in TiC_(x)O_(y) in the substrate 13(sintered body) forming each bar 100B is not more than 0.3, thepolishing rate of the substrate 13 forming the bar 100B tends to becomelow in the lapping step, whereby the level difference can be madebetween the substrate 13 and the laminate 14. In contrast to it, sincethe ratio y falls within the range of 0.3<y≦0.52 in the presentembodiment, it is easier to increase the polishing rate of the substrate13 and thereby to reduce the level difference between the substrate 13and the laminate 14 than in the case where the ratio y is not more than0.3.

After the lapping step, the air bearing surface S is subjected to ionmilling being a kind of dry etching, to form the air inlet groove 11 a(not shown) in the air bearing surface S.

If the substrate 13 (sintered body) forming each bar 100B consists ofthe two phases of the phase of Al₂O₃ and the phase of TiC_(x)O_(y),chipping becomes more likely to occur during the cutting step. Incontrast to it, since the substrate 13 (sintered body) in the presentembodiment further has the phase of Al—Ti—O in addition to the twophases of the phase of Al₂O₃ and the phase of TiC_(x)O_(y), chipping canbe suppressed with more certainty than in the case where the substrate13 does not include the phase of Al—Ti—O.

If the substrate 13 (sintered body) forming the bar 100B furtherincludes the phase of carbon in addition to the three phases of thephase of Al₂O₃, the phase of TiC_(x)O_(y), and the phase of Al—Ti—O,there are crystal grains of carbon (graphite) as well as the crystalgrains of Al₂O₃, the crystal grains of TiC_(x)O_(y), and the crystalgrains of Al—Ti—O in the air bearing surface S. When such an air bearingsurface S is subjected to ion milling, it is hard to evenly etch thewhole air bearing surface S and the air bearing surface S after the dryetching tends to be unlikely to smooth. The inventors believe that theabove phenomenon is caused for the following reasons: easiness to etchthe sintered body by ion milling is dependent on hardness of crystalsforming the sintered body; and the crystal phase of carbon (graphite)being soft with low hardness is etched too quickly by ion milling.

In contrast to it, the substrate 13 (sintered body) in the presentembodiment consists of the three phases of the phase of Al₂O₃, the phaseof TiC_(x)O_(y), and the phase of Al—Ti—O without inclusion of the phaseconsisting of carbon, the whole air bearing surface S is more evenlyetched and the air bearing surface S after the ion milling becomes moresmoothed, than in the case where the sintered body includes the phaseconsisting of carbon.

After the ion milling, each bar 100B is cut at appropriate positions sothat each piece includes a thin-film magnetic head 10; whereby we canobtain a plurality of magnetic head sliders 11 each having the thin-filmmagnetic head 10. Before or after this cutting step, the air bearingsurface may be further coated with a layer of DLC or the like.

The above-described production method of the magnetic head slider 11 ofthe embodiment enables the smooth air bearing surface S to be formed,for example, even in cases where femto-sliders or much smaller slidersare formed in order to be mounted on downsized HDDs, and permits us toobtain the magnetic head slider 11 fully adaptable for reduction in thefly height.

The present invention will be described below in further detail withexamples thereof, but it should be noted that the present invention isby no means intended to be limited to these examples.

Examples 1-14 and Comparative Examples 1-4 Production of Sintered Body

First, the raw material powder was prepared by mixing the Al₂O₃ powder(average grain size: 0.5 μm), the TiC powder (average grain size: 0.5μm), and the TiO₂ powder (average grain size: 0.3 μm). The respectivecontents (unit: % by mass) of the Al₂O₃ powder, the TiC powder, and theTiO₂ powder in the raw material powder and the mass ratio of the TiCpowder to the Al₂O₃ powder (TiC/Al₂O₃) were set to be the values shownin Table 1.

Next, the raw material powder was pulverized and mixed with IPA(isopropyl alcohol; boiling point 82.4° C.) in a ball mill for 30minutes and thereafter the mixture was granulated by spray granulationat 150° C. in a nitrogen atmosphere to obtain granules. The resultantgranules were primarily compacted by cold press to obtain a compact. Inthe cold press, the granules were compressed under the pressure of about5 MPa (50 kgf/cm²)

Thereafter, the compact was fired for two hours by hot press to obtainthe sintered body in each of Examples 1 to 14 and Comparative Examples 1to 4. In the hot press, a firing atmosphere was vacuum. The firingtemperature and the pressure (kgf/cm²) on the compact by hot press wereset to be the values shown in Table 1.

TABLE 1 Raw material powder Mass Hot press ratio (—) Firing PressureContent (mass %) TiC/ temperature (kgf/ Al₂O₃ TiC TiO₂ Al₂O₃ (° C.) cm²)Comparative 52.6 31.5 15.9 0.60 1600 67 Example 1 Example 1 52.6 31.515.9 0.60 1600 100 Example 2 52.6 31.5 15.9 0.60 1450 133 Example 3 52.631.5 15.9 0.60 1500 133 Example 4 52.6 31.5 15.9 0.60 1550 133 Example 552.6 31.5 15.9 0.60 1600 133 Example 6 52.6 31.5 15.9 0.60 1600 190Comparative 52.6 31.5 15.9 0.60 1600 267 Example 2 Comparative 52.6 31.515.9 0.60 1500 400 Example 3 Example 7 57.5 34.5 7.9 0.60 1500 133Example 8 50.1 30.0 19.9 0.60 1500 133 Example 9 55.0 33.0 12.0 0.601600 100 Example 10 63.0 21.0 16.2 0.33 1500 133 Example 11 58.0 26.015.9 0.45 1500 133 Example 12 50.0 34.0 15.9 0.68 1500 133 Example 1348.5 35.7 15.8 0.74 1500 133 Example 14 47.5 28.5 24.0 0.60 1500 133Comparative 45.0 27.0 28.0 0.60 1500 67 Example 4

[Evaluation of Characteristics]

(Check on Composition of Sintered Body)

The compositions of the respective sintered bodies of Examples 1 to 14and Comparative Examples 1 to 4 were measured by TEM-EDS mapping. Table2 provides the compositions of the sintered bodies confirmed by themeasurement.

TABLE 2 Peak area Lattice Polishing Profile y ratio constant rateirregularity Chipping Composition of sintered body — — pm % — —Comparative Al₂O₃ + TiC_(x)O_(y) 0.41 1.73 430.2 174 A A D Example 1Example 1 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) 0.35 1.76 431.0 171 A A AExample 2 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) 0.31 1.72 430.7 180 A A AExample 3 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) 0.33 1.77 431.1 182 A A AExample 4 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) 0.31 1.76 430.6 167 A A AExample 5 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) 0.32 1.83 430.8 167 A A AExample 6 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) 0.34 1.85 431.0 162 A A AComparative Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) + C 0.25 1.77 431.1 180 A DA Example 2 Comparative Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O) + C 0.23 1.69431.7 189 A D A Example 3 Example 7 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.15 1.80 432.0 101 C A B Example 8 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.40 1.71 429.7 180 A A A Example 9 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.32 1.77 431.4 122 B A B Example 10 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.34 1.01 431.0 120 B A B Example 11 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.32 1.30 431.6 132 B A A Example 12 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.31 1.90 431.3 161 A A A Example 13 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.30 2.18 431.5 115 B A C Example 14 Al₂O₃ + TiC_(x)O_(y) + (Al—Ti—O)0.52 1.71 428.5 170 A A B Comparative Al₂O₃ + TiC_(x)O_(y) — — — — — — —Example 4

As seen from Table 2, it was confirmed that each of the sintered bodiesof Examples 1 to 14 consisted of the three phases of the crystal phaseof Al₂O₃, the crystal phase of TiC_(x)O_(y), and the crystal phase ofAl—Ti—O. It was also confirmed that in Examples 1 to 14, 0.5<x+y≦1, x>0and y>0. On the other hand, it was confirmed that the sintered body ofComparative Example 1 consisted of the two phases of the crystal phaseof Al₂O₃ and the crystal phase of TiC_(x)O_(y). It was also confirmedthat the sintered bodies of Comparative Examples 2 and 3 consisted offour phases, the crystal phase of Al₂O₃, the crystal phase ofTiC_(x)O_(y), the crystal phase of Al—Ti—O, and the crystal phase ofgraphite.

In Comparative Example 4, the compact was deformed during the hot pressof the compact in the production process of the sintered body and theshape of the sintered body was not the desired one suitable forproduction of the magnetic head slider. Therefore, for the sintered bodyof Comparative Example 4, measurement was not carried out as to the peakarea ratio, lattice constant, polishing rate, chipping, and profileirregularity after ion milling described below.

(Measurement of Peak Area Ratio of TiC_(x)O_(y)/Al₂O₃)

For each of the sintered bodies of Examples 1 to 14 and ComparativeExamples 1 to 3, the measurement by XRD was carried out and the peakarea ratio TiC_(x)O_(y)/Al₂O₃ of TiC_(x)O_(y) to Al₂O₃ was calculated.The results obtained are provided in Table 2.

(Measurement of Lattice Constant of TiC_(x)O_(y))

Each of the lattice constants of TiC_(x)O_(y) in the respective sinteredbodies of Examples 1 to 14 and Comparative Examples 1 to 3 wascalculated based on the X-ray measurement using Si of the standardsample, as described above. The results obtained are provided in Table2.

(Measurement of Polishing Rate)

A piece of about 20×20×1.8 mm was cut out from each of the sinteredbodies of Examples 1 to 14 and Comparative Examples 1 to 3, and thepiece was lapped with a single-side polisher using a slurry containingdiamond particles having the diameter of 0.1 μm. The polishingconditions herein were as follows: the number of rotations of a tinplate 37.5 rotations/min; load 2550 g; the number of rotations of anoscar motor 55 rotations/min; polishing time 10 minutes. A polishingspeed (unit: μm/10 min) of each of the sintered bodies of Examples 1 to14 and Comparative Examples 1 to 3 was acquired by measuring thicknessesbefore and after the polishing, and dividing a difference thereof by thepolishing time. Then the polishing speed was divided by a referencespeed of 1.2 μm/10 min, thereby obtaining polishing rates (unit: %) ofthe respective sintered bodies of Examples 1 to 14 and ComparativeExamples 1 to 3. The results are provided in Table 2. In Table 2, thepolishing rates are evaluated based on the following criteria: “A” for apolishing rate of not less than 150; “B” for a polishing rate between110 inclusive and 150; “C” for a polishing rate between 100 inclusiveand 110. The polishing rate is preferably as large as possible andpreferably A, B, or C.

(Measurement of Profile Irregularity after Ion Milling)

Each of the sintered bodies of Examples 1 to 14 and Comparative Examples1 to 3 was lapped by the aforementioned method to form a polishedsurface, the polished surface was then subjected to ion milling, andsurface roughness Ra (profile irregularity) was measured in the polishedsurface after the ion milling (dry etched surface). The results areprovided in Table 2. In Table 2, the profile irregularities areevaluated based on the following criteria: “A” for a profileirregularity of not more than 10 nm; “D” for a profile irregularity ofmore than 10 nm. The smaller the profile irregularity, the smoother thedry etched surface is. Therefore, the profile irregularity is preferablyas small as possible.

(Evaluation of Chipping)

Each of the sintered bodies of Examples 1 to 14 and Comparative Examples1 to 3 was evaluated as to chipping by the method described below.First, a test piece of about 57.6 mm×10 mm×1.2 mm was cut out of eachsintered body. Then each test piece was cut at 9500 rpm and at a feedrate of 100 mm/min, using a dicing blade (outside diameter 54 mm×insidediameter 40 mm×thickness 0.2 mm) available from DISCO Corporation, andthereafter the test piece thus cut was observed at the magnification of2000× with an optical microscope to check whether chipping occurred nearthe cut surface of the test piece. The results of the evaluation ofchipping are provided in Table 2. In Table 2, the chipping was evaluatedbased on the following criteria: “A” for a sintered body wherein chipsare less than 5 μm; “B” for a sintered body wherein a rate of chipsbetween 5 and 10 μm relative to a total count of observed chips is lessthan 5%; “C” for a sintered body wherein a rate of chips between 5 and10 μm relative to a total count of observed chips is not less than 5%;“D” for a sintered body wherein chips exceed 10 μm. The result of theevaluation of chipping is preferably A, B, or C.

As shown in Table 2, it was confirmed that in Examples 1 to 14 thepolishing rate was high, the profile irregularity was small, and thechipping was unlikely to occur. It was confirmed on the other hand thatin Comparative Example 1 the chipping was more likely to occur than inExamples 1 to 14. It was further confirmed that in Comparative Examples2 and 3 the profile irregularity was larger and the dry etched surfacewas less smooth than in Examples 1 to 14.

It was also confirmed that in Examples 1-6, 8-12, and 14 where0.3<y≦0.52 among Examples 1 to 14, the polishing rate was higher than inExample 7 where y was not more than 0.3 and the chipping was less likelyto occur than in Example 13 where y was 0.3.

1. A sintered body consisting of: Al₂O₃; a compound represented by thechemical formula (1) below; and a composite oxide containing Al and Ti,TiC_(x)O_(y)  (1) wherein x+y≦1, x>0 and y>0.
 2. The sintered bodyaccording to claim 1, wherein 0.3<y≦0.52.
 3. A method for producing asintered body, comprising a step of hot pressing a raw material powdercontaining Al₂O₃, TiC and TiO₂, under a pressure in the range of 100 to200 kgf/cm².
 4. The method according to claim 3, wherein a content ofsaid TiO₂ in the raw material powder is in the range of 12 to 24% bymass.